I remember reading about SW's feelings on the odd-numbered albums versus the even-numbered ones, and immediately thought about the Star Trek films, where in fans say the even ones are the better ones (Wrath of Khan, Voyage Home, Undiscovered Country, First Contact...though Nemesis wasn't that great IMO), and the odd-numbered ones were pretty meh.
I suppose for Porcupine Tree, it'd be the opposite, and I tend to agree. After the first two albums, the even ones are almost all of my favorites - The Sky Moves Sideways, Stupid Dream, In Absentia, and Fear Of A Blank Planet are easily my Top 4 PT albums, I think, or at least in the top half (maybe with Deadwing in there, too). Oddly enough, those four albums all have a significant amount of blue on their album covers (coincidence?). The evens, however, have more of a reds/browns/yellows hue to them, with the last two being more muted and in greys, which is odd, especially in contrast to the blue-ish albums between them.
-Marc.